Program: Basic HashSet Operations.

Below example shows basic operations on HashSet object like creating object, adding elements, verifying whether the hashset is empty or not, removing an element, size of the hashset, and to check whether an object exists or not.

package com.java2novice.hashset;

import java.util.HashSet;

public class MyBasicHashSet {

	public static void main(String a[]){
		HashSet<String> hs = new HashSet<String>();
		//add elements to HashSet
		hs.add("first");
		hs.add("second");
		hs.add("third");
		System.out.println(hs);
		System.out.println("Is HashSet empty? "+hs.isEmpty());
		hs.remove("third");
		System.out.println(hs);
		System.out.println("Size of the HashSet: "+hs.size());
		System.out.println("Does HashSet contains first element? "+hs.contains("first"));
	}
}

[second, third, first]
Is HashSet empty? false
[second, first]
Size of the HashSet: 2
Does HashSet contains first element? true